The invention relates preferably to a surface covering product suitable for use in the furniture and construction industry, furthermore to a process and apparatus for its production.
Surface covers are made by a conventional method with the use and jointed assembly of strips or laths having a straight and/or curved-jointed surface, and produced with a continuous extrusion from the mixture of colouring agents added to the melt of thermoplastic synthetic materials according to processes known in the synthetic industry. Such variation of the process is also known, when batches of the melt to be extruded are colored differently, then the batches are interfused proportionately and this way the strips or laths obtain a characteristically grained pattern imitating or resembling the grain of wood. A drawback of the processes is that the appearance of the surface of the finished product is monotonous, thus they meet only modest aesthetic demand. On the other hand an advantage of the process is that the laths extruded from synthetic material preferably from hard PVC, are accurate to dimension, solid despite their length, and not inclined to dimension variation and warping.
There are processes in the wood working industry, when long laths are sawn from timber (planks and boards), planed, followed with cutting various articulations into the surface of the laths, and the so-formed surfaces are coated with lacquers. This process is also disadvantageous, because strips or laths of limited length, not longer than 3 m can be produced from the valuable--and aesthetically pleasing--wood types with short log, and in addition the material lost be planing and cutting during the process is considerable generally exceeding 40%. Thus the laths (e.g. wall covering laths) made of valuable hard woods (e.g. oak, walnut, cherry, etc.) are very expensive. In addition the proportion of laths warped and unsatisfactory in respect of the surface quality is high, and moreover the warping and grain parting on the surface occurring after fitting on as a result of the subsequent dampness render the final quality uncertain. A further drawback is that no mass production of laths longer than 2.5 m is possible without junction.
There are processes in the wood working industry, when the natural wood of poor quality or the artificial wood varieties are covered with veneers of high technical and aesthetic value by use of sticking--laminating processes. A drawback of this process is that the balanced behavior of wood layers with varying stress-content, i.e. the formation of long laths free from warping is difficult and the uneven wettness effects ensuing in the course of application--despite the costly process--will cause generally known deformation. Such solution is described for instance by Roland Siebert in his book: "Mobelbau" (Verbesserte 2. Auflage, Leipzig, GDR).
The cost of the process is increased by the fact, that compliance with the principle of symmetry is necessary at the laminations, in order to avoid warping. Thus the sticking of plywood onto the backside is also necessary, despite that from an aesthetic and functional point of view this layer represents unnecessary use of material, additional work and cost.
The wood or artificial wood layers destined for ensuring the strength and trueness to shape are always prone to deformation, which as a drawback is characteristic to the above processes and products.
As a result of the listed adverse characteristic none of the synthetic materials and wood veneers is suitable to meet the different demands of the furniture and construction industry, to such extent, that they could have been used separately and generally in the two different kinds of industrial fields.
The invention is aimed at elimination of the above shortcomings, i.e.--by special jointing process of the two different types of material--to produce a product of such property and quality, which is equally applicable in both industrial fields and meets their several demands, which is useable as a structural material, surface covering product, ornamental cover and for other decoration purposes in the furniture and construction industry. Furthermore it is resistant to stress as well as a wood substitute to a great extent.